Water Resources Management in the Ganges Basin: A Comparison of Three
Strategies for Conjunctive Use of Groundwater and Surface Water
Mahfuzur R. Khan, Clifford I. Voss, Winston Yu, and Holly A. Michael*
Journal: Water Resources Management
(*) Corresponding Author:
Holly A. Michael
Department of Geological Sciences
Department of Civil and Environmental Engineering
University of Delaware
255 Academy Street, Newark, DE 19716, USA
Email: hmichael@udel.edu
A-1 Introduction
This document contains supplementary materials for the article, “Water Resources Management
in the Ganges Basin: A Comparison of Three Strategies for Conjunctive Use of Groundwater and
Surface Water”. Section A-2 presents the synthesis of hydrological data collected from various
sources. In section A-3, delineation of different type areas for the GWM (Ganges Water
Machine) strategy is presented. The temporal development of hydraulic head at different location
from the infiltrating river/canal for the base case, and the effects of vertical anisotropy on the
storage for the sensitivity simulations are discussed in section A-4. In section A-5, GWM
simulation results for each type area are presented in a table. Additionally, the temporal
development of actual groundwater recharge from rainfall, irrigation return flow, and existing
canal seepage for GWM is shown in a figure (Figure ESM-6). A hydrological budget in UP is
presented in Section A-6. Temporal development of infiltration rates for the GWM and PAC
(Pumping Along Canals) strategies are presented in Section A-7.
A-2 Hydrogeological Parameters
The average horizontal (Kh) and vertical (Kv) hydraulic conductivity were determined by
simulating flow through a hypothetical heterogeneous aquifer system (Figure ESM-1)
constructed based on published lithological cross-sections and fence-diagrams (Chaturvedi and
Ramakrishna 1983; Umar et al. 2001) and reported values of Kh of the aquifer sediments in
different areas within UP (e.g. Ala Eldin et al. 2000; Umar et al. 2001; Umar 2006; Rao et al.
2007; Umar et al. 2008; Raut 2009; Singh et al. 2009; Umar and Ahmed 2009). The simulated Kh
and Kv were 15 m/d and 0.15 m/d, respectively, through the heterogeneous field, indicating that
the coefficient of anisotropy (Kh/ Kv) is approximately 100 on the vertical scale of 300 m. The
basin-wide average values of specific yield (0.16) reported in Government of India (1997) were
used.
Fig. ESM-1 Postulated aquifer system simulated in this study to determine the effective horizontal and
vertical hydraulic conductivity in UP
The UP aquifers receive recharge from rainfall, irrigation return flow, and canal seepage.
Groundwater recharge from each of these sources was estimated using criteria established by the
Government of India (1997). A forty-year record of monthly average rainfall data (World Bank
unpublished) was used to estimate the recharge from rainfall. Estimated recharge rates during the
monsoon season vary between 11 cm and 25 cm from west to east, with a spatial average of 15
cm. Dry season recharge from rainfall is much less and occurs relatively uniformly (2 cm to 4 cm
during the dry season) over UP. Recharge from irrigation return flow was estimated using the
data on irrigation areas existing during 1996-97 (Irrigation Department 1996-1997). There are
two main cropping seasons in UP, namely the Kharif (wet season crop) and the Rabi (dry season
crop). It was assumed that the irrigation activity remains constant for both cropping seasons.
Recharge from irrigation during each cropping season varies from less than 5 cm in the north and
southeast to over 10 cm in the west. These two sources provide a combined monsoon season
recharge that ranges from 20 cm to over 30 cm over the basin, with a spatial average of 25 cm
per season. Similarly, the combined non-monsoon recharge, which is mainly from irrigation,
varies from less than 5 cm to more than 12 cm with a spatial average of 10 cm. Groundwater
recharge from canals was estimated using GIS data of major canals (World Bank unpublished)
and assuming a 35 m average width of the major canals. Based on canal density, UP was
subdivided into a number of sub-basins; then groundwater recharge from canals per unit area of
each sub-basin was estimated. The estimated canal recharge in canal irrigation areas varies from
2 cm/year to 10 cm/year depending on the canal density. When applied to the entire State, the
estimated annual canal recharge is 4.5 billion m3. This recharge is added to the rainfall recharge
in the model. This estimated total potential recharge for the 4-month wet season and 8-month dry
season were simulated in the model using the MODFLOW Recharge package. In the model, each
year was divided into two stress periods corresponding to the seasons.
The Ganges and most of its UP tributaries are perennial and closely connected to the
underlying aquifers (National Institute of Hydrology 1999). Assuming that 80% of annual flow
occurs during dry season, the average annual monsoonal and dry season flow at the UP-Bihar
boundary (excluding the Gandak River) would be about 240 BCM and 60 BCM, respectively
(World Bank unpublished). This dry season flow is from three sources: (1) snowmelt, surface
water, and groundwater in the headwater region in the Himalaya in the north (Andermann et al.
2012), (2) surface water and groundwater in the hills and highlands in the south, and (3)
baseflow from groundwater within UP. There is no primary estimate of baseflow in UP. A
numerical modeling estimate (World Bank unpublished) suggests that shallow groundwater in
UP contributes about 13 billion m3 of the dry season river flow. This amount is considered here
as the total baseflow for UP rivers. This amount is required to return to the river downstream of
the pumping section to maintain the dry season flow downstream. For GWM, this amount is
required in addition to the upstream flow already routed from the upstream section of the well
fields to the downstream section to maintain the dry season flow downstream.
River widths and the spacing between adjacent rivers were estimated using GIS data of the
Ganges and its tributaries. River widths in the basin vary widely, from a few hundred meters to
more than 1000 m. In general, however, stream widths increase downstream as new tributaries
join the main channels. The distance between major tributaries of the Ganges ranges from 30 km
to more than 60 km.
A-3 Type Area Delineation for the Ganges Water Machine strategy
Different type areas for the GWM strategy were determined based on the spatial distribution of
the aquifer width, river width, and recharge from existing canals that vary considerably over UP
(Table ESM-1). Eight distinct type areas were delineated (Figure ESM-2).
Fig. ESM-2 Type areas for GWM in UP. Total type-area length is approximately 3000 km
Table ESM-1 Attributes of type areas
Type
area
River
width
[m]
Recharge
from canals
[cm/year]
1
2
3
4
5
6
7
8
300
300
300
300
600
600
900
900
0
2
6
10
0
6
2
10
Distanc
e
betwee
n rivers
[km]
60
30
60
60
60
60
60
60
A-4 Temporal Head Development and the Effect of Anisotropy for the Sensitivity Analysis
Figure ESM-3 shows the temporal development of hydraulic heads at different locations in the
aquifer relative to the infiltrating water body i.e. river/canal for the base case simulation. Figure
ESM-3 indicates that the hydraulic heads reach a dynamic steady-state after a few decades of
pumping, with seasonal head fluctuations decreasing with distance from the river. Water table
configuration at different time interval during the monsoon season is shown in Figure ESM-4 for
the same simulation at dynamic steady-state. Changes in the pre-monsoon head and storage
volume at the dynamic steady-state in response to the change in different aquifer parameters are
summarized in Table ESM-2.
Fig. ESM-3 Hydraulic head vs. time at locations relative to the river. The head data is obtained at the
middle of the pumping depth (100 m)
Fig. ESM-4 Water table elevations at different time intervals after the onset of monsoon infiltration.
Figure ESM-5 shows the temporal development of seasonal groundwater storage and the
development of a new dynamic steady-state for different values of aquifer vertical anisotropy.
The time required to reach a new dynamic steady-state increases with increasing anisotropy.
Fig. ESM-5 Annual storage volume with time for three values of anisotropy
Table ESM-2 Sensitivity analysis results. Effects of parameter variations on monsoonal storage volume
and steady-state water table depth at the depth and location of the pumping wells. All values correspond
to dynamic steady-state conditions and storage volume is per km length of river. Pre-monsoon head is the
simulated maximum head at a distance of 3 km from the river and at a depth of 100 m below surface.
Changes (Δ) are given as % of the base case estimates, negative indicates a decrease
Storage
[MCM/a*]
Parameter Variations
Base case*
Factors related to
Factors related to
Premonsoon
head [m]
-34
 Pre-monsoon
head [%]
Time to reach
dynamic steadystate (years)
< 50
22
50% higher recharge
20
-9
-30
12
< 35
50% lower recharge
22
0
-40
-18
NA*
2x River Width
22
0
-27
21
< 35
groundwater
recharge
 Storage
[%**]
3x Aquifer Width
16
-27
-22
35
< 35
10x higher riverbed cond.
22
0
30
1
<35
10x lower riverbed cond.
50% higher Sy
2.2
22
-90
0
-225
-29
-560
15
NA
< 50
50% lower Sy
22
0
-47
-38
< 35
10x higher K
22
0
-11
68
< 20
10x lower K
16
-27
-131
-285
NA
10x lower Kv
22
0
-49
-44
50
100x lower Kv
18
-18
-105
-209
NA
Isotropic
groundwater flow
Anisotropic
*million m3 per year
**NA: Dynamic steady-state was not achieved within the 50 year simulation period.
A-5 GWM Simulation Results for Different Type Areas
The storage and pumping rate per kilometer river length for three different design pre-monsoon heads were simulated for the GWM
scheme. The total annual storage for each type area was estimated by multiplying that by the total well-field length and by two (to
include both sides of each river) (Table ESM-3).
Table ESM-3 Pumping rates and resulting storage per kilometer length of river for individual type areas and the total for the basin for GWM and
the hydrogeologic model described in Section A-2.
Type 30 m design pre-monsoon head at dynamic steady-state in
area
the well-field center
Total
Pumping
Storage well-field
rate
[MCM /a] length
[MCM/a]
[km]
Total
annual
pumping
[BCM]
50 m design pre-monsoon head at dynamic
steady-state in the well-field center
Total annual Pumping
Total annual Total Annual
Storage
storage
rate
pumping
storage
[MCM /a]
[BCM]
[MCM /a]
[BCM]
[BCM]
80 m design pre-monsoon head at dynamic steadystate in the well-field center
Pumping rate
[MCM /a]
Storage
[MCM /a]
Total
Total annual
annual
pumping
storage
[BCM]
[BCM]
1
17.3
4.7
310
5.4
1.5
24.0
7.9
7.4
2.5
33.6
12.9
10.4
4.0
2
16.8
4.7
220
3.8
1.0
20.0
7.9
4.5
1.8
26.0
12.9
5.9
2.9
3
19.2
4.7
650
12.5
3.0
26.0
7.9
16.9
5.1
35.5
12.9
23.0
8.4
4
20.0
4.7
460
9.2
2.2
27.0
7.9
12.4
3.6
36.5
12.9
16.8
5.9
5
19.2
6.2
300
5.9
1.9
26.9
10.3
8.2
3.1
38.0
17.0
11.6
5.2
6
20.6
6.2
690
14.1
4.3
28.3
10.3
19.4
7.0
39.5
17.0
27.3
11.7
7
20.6
8.0
180
3.6
1.4
29.3
14.4
5.1
2.5
41.4
23.5
7.3
4.1
8
23.0
8.0
180
4.0
1.4
33.6
14.4
5.9
2.5
48.0
23.5
8.4
4.1
~ 3,000
58
17
80
28
110
46
Total
Figure ESM-6 shows the temporal development of groundwater recharge for different design
head scenarios of GWM. The vertical axis presents the actual groundwater recharge from
rainfall, irrigation return flow, and existing canal seepage as a percentage of the potential
recharge applied in the model top boundary using MODFLOW Recharge package.
Fig. ESM-6 Actual groundwater recharge with time as percentage of potential recharge applied in the
GWM model for different design head scenarios
A-6 Water Budgets and Allocation
In UP, most of the domestic water supply is from groundwater. Currently, the total annual
domestic and industrial water demand in UP is about 10 billion m3 (Planning Commission 2007).
Considering 50% consumptive use (Planning Commission 2007), the net requirement is 5 billion
m3 .
Water loss due to evaporation and canal seepage occurs during water transportation via
canals. The mean annual evaporation rate in the UP region ranges from 200 cm/year to 250
cm/year (Jain et al. 2007). When the existing canal networks are considered (see section 2.2.4),
there are approximately 500 m2 of canal surface area per km2 of irrigated land. If the entire 12
Mha of irrigated land is brought under such canal networks, the canal surface area would be
about 600 million m2. The total loss due to evaporation during the dry season would be less than
2 billion m3. Because DPR (Distributed Pumping and Recharge) involves pumping at the point
of use, there would be little or no transport of the pumped water during the dry season.
Therefore, the dry season evaporation loss from canals is assumed to be zero for this strategy.
This study assumes lined canals for water transportation, therefore the water loss due to canal
seepage is considered zero for all the strategies except GWM, for which seepage from existing
canals is included in the model as groundwater recharge. Therefore, in addition to evaporative
loss from canals, there is also canal seepage loss for GWM. This is added to GWM models as 4.5
billion m3 of groundwater recharge.
Loss of river baseflow would vary with the elevation of pre-monsoon water table under
different strategies. The entire baseflow within river channels with pumping (13 billion m3)
would be lost under the GWM scheme since these reaches would be dry during the pumping
season. Simulated dynamic steady-state heads for the PAC vary between -12 m and -15 m, but in
reality, the water table will be shallower near the river, which is a recharge boundary. PAC
pumping may reduce the magnitude of the dry season head gradient between the aquifer and the
river but is unlikely to reverse it (see Figure 4b). It is therefore assumed in this work that half of
the baseflow loss (one half of 13 billion m3) would occur under PAC due to the changes in head
gradient near the river. Currently, the pre-monsoon water table depth is less than 5 m in the canal
irrigation areas (Raut 2009) and 12 m - 20 m in the groundwater irrigation areas (World Bank
2010). The current study assumes that DPR maintains a more uniform water table less than 10 m
below ground surface by introducing groundwater pumping in the existing canal irrigation areas.
This water table depth would change over the year, which could cause a reduction in baseflow in
the existing canal irrigation areas. However, the reduction would be insignificant compared to
that caused by GWM and PAC because the induced drawdown is relatively small. Moreover,
where pumping is distributed rather than located near the rivers, only a portion of the total annual
stream-flow depletion would occur during the pumping season (Bredehoeft 2011). Therefore,
this study assumes a negligible baseflow depletion for DPR.
A-7 Temporal Development of Infiltration Rate for the GWM and PAC Strategies
Figure ESM-7 shows the simulated infiltration rates over the 120 days of the monsoon season for
different design pre-monsoon steady-state head conditions for the GWM strategy with different
river widths (a, b, and c), and for the PAC strategy (d). For the GWM, the riverbed conductance
was adjusted so that in all cases the maximum infiltration capacity of the river equals that of the
Revelle and Lakshminarayana (1975). In all cases, the river infiltration rate decreases with time,
the greatest reduction in the specific infiltration rate over time occurs in the case of wider rivers,
while for the PAC the infiltration rate remains fairly constant throughout the monsoon season.
Fig. ESM-7 Infiltration rate through riverbeds as a function of time during the monsoon season for
different river geometries of GWM. (a) 300 m wide river, (b) 600 m wide river, and (c) 900 m wide river,
and (d) for PAC.
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